The present invention relates, in general, to processes for manufacturing cellulosic paper products and, more particularly, to such processes which provide cellulosic base sheets or finished products (e.g., hand towels) that release reduced malodor upon re-wetting.
Commercial paper products such as hand towels are manufactured from cellulosic base sheets. A cellulosic base sheet is a paper product in its raw form prior to undergoing conventional post-treatments such as calendaring and embossing. In general, cellulosic base sheets are made by preparing an aqueous suspension of papermaking fibers and injecting or depositing the suspension onto an endless sheet-forming fabric to form a wet-laid web, which is then dewatered and dried to produce a base sheet suitable for finish processing.
Because of its commercial availability and practicality, through-drying is often used to dry base sheets. Through-drying involves removing water from a wet-laid web by passing a heated gas (e.g., air) through the web. More specifically, through-air drying typically comprises transferring a partially dewatered, wet-laid web from a sheet-forming fabric to a coarse, highly permeable through-drying fabric. A stream of heated air is passed through the wet web carried on the through-drying fabric as it runs over the high permeability rotating cylinder or drum of a through-drying apparatus. As the hot, dry air contacts the wet web, water is evaporated from the web and is transferred to the flow of drying air. Processes for making cellulosic base sheets including through-drying are described, for example, in U.S. Pat. No. 5,607,551 (Farrington et al.) and U.S. Pat. No. 6,149,767 (Hermans et al.), the entire disclosures of which are incorporated herein by reference.
It has been observed that a strong, burnt popcorn-like odor is sometimes emitted from finished paper hand towels when the towels are wetted (i.e., re-wetted after final drying of the base sheet from which the towel is made). Upon investigation, this problem of malodor release has been found to be particularly present in paper products made from cellulosic base sheets that have been through-air dried at relatively high air temperatures. It was hypothesized that over-drying or over-heating of the base sheets was leading to the malodor problem upon re-wetting of the paper product. By operating the through-air drying stage of a base sheet manufacturing process at a lower air temperature and compensating with slightly longer sheet residence time on the drying drum, the malodor problem can be largely eliminated. However, longer residence times in the through-drying apparatus adversely affect the overall productivity of the base sheet manufacturing process.
Therefore, what is lacking and needed in the art is a process which can reduce or eliminate malodor released upon re-wetting of paper products, particularly those made from through-air dried cellulosic base sheets, while allowing higher air drying temperatures and shorter dryer residence times to be used to increase product throughput and productivity.
Among the several objects of the present invention, therefore, is the provision of a process for manufacturing a cellulosic paper product from a wet-laid web; the provision of such a process wherein the paper product exhibits a reduced malodor upon re-wetting; the provision of such a process wherein the wet-laid web can be through-air dried at higher temperatures and shorter dryer residence times; the provision of such a process wherein productivity and throughput of the manufacturing process are increased; and the provision of such a process which is relatively inexpensive and easy to implement.
Briefly, therefore, the present invention is directed to a process for manufacturing a cellulosic paper product comprising forming an aqueous suspension of papermaking fibers, depositing the aqueous suspension of papermaking fibers onto a sheet-forming fabric to form a wet web and through-drying the wet web by passing a heated gas through the web. In accordance with the present invention, a vanilla compound is introduced into the aqueous suspension of papermaking fibers. The vanilla compound can be introduced into the aqueous suspension of papermaking fibers before or after the suspension is deposited onto the sheet-forming fabric. In accordance with a more particular embodiment of the present invention, the vanilla compound is introduced into the aqueous suspension of papermaking fibers in a solution containing a vanilla bean extractive and ethyl alcohol (e.g., vanilla bean extract), the aqueous suspension of papermaking fibers is deposited onto the sheet-forming fabric to form the wet web after introduction of the vanilla compound and the wet web is through-dried by passing air heated to a temperature of at least about 175xc2x0 C. through the wet web.
Other objects and features of the present invention will be in part apparent and in part pointed out hereinafter.